The present invention relates to a calculus crushing apparatus for crushing a calculus produced in a body cavity. A calculus produced in internal organs such as a bile duct or a urinary bladder adversely affects a patient. Especially, an enlarged calculus gives much pain to a patient. Therefore, a calculus crushing apparatus is inserted in a body cavity through an endoscope and crushes the calculus produced in the body cavity to remove it from the body or removes it without crushing.
A calculus crushing apparatus of this type includes a sheath having a hard portion at its distal end and inserted in a body cavity with an endoscope, an operation wire inserted in the sheath, and a basket constituted by a plurality of elastic wires and fixed at the distal end of the operation wire. A connecting rod is fixed to the proximal end of the operation wire and is reciprocated by an operation section to expand or contract the basket. In crushing a calculus, after the calculus is held inside the basket projected from the distal end of the sheath, the basket is retracted inside the sheath and contracted by the operation portion, so that the calculus is crushed into pieces by the basket.
If a calculus held inside the basket is very hard, a very large tension acts on the basket, operation wire, and connecting rod when the basket is retracted inside the sheath. For this reason, the elastic wires of the basket or the operation wire may be disconnected midway therealong by the tension. When the elastic wires are disconnected, the wall of the body cavity is damaged by disconnected portions. On the other hand, when the operation wire is disconnected midway therealong with the calculus held inside the basket, the basket and the part of the operation wire cannot be pulled outside the body cavity and remain therein, thereby posing a serious problem.